Luke 9:39
And, lo, a spirit taketh him, and he suddenly crieth out; and it teareth him that he foameth again, and bruising him hardly departeth from him.
Cross-reference
Luke 9:42 immediately continues the story as the demon throws the boy again — confirming the violent pattern described earlier.
Luke 4:35 depicts Jesus rebuking a demon that throws a man down—similar violent manifestation as the boy's convulsions here.
Luke 8:29 describes a demon-possessed man seized and breaking chains—mirrors the boy's violent seizures in this verse.
Mark 9:20 is the parallel account: the spirit convulses the boy, causing him to foam at the mouth.
Mark 9:26 describes the spirit's final convulsion and exit—parallel to the action described here.
Mark 1:26 shows a similar demonic convulsion and cry — both depict the same violent manifestation of an unclean spirit.
Mark 9:18 is the parallel account of this same demon possession — identical description of seizing, foaming, and convulsions.